In recent years, in an image forming apparatus such as a printer or a digital multifunction peripheral, a demand for reduction in unnecessary power consumption has increased. To achieve such a demand, there has been known a method in which the power consumption of the image forming apparatus is decreased by reducing or cutting off power supply to a main control unit in the image forming apparatus when the image forming apparatus does not operate for a predetermined period of time, while supplying power to a communication unit in the image forming apparatus. Japanese Patent Application Laid-Open No. 2009-151537 discusses a method of responding, when the communication unit receives a packet sent from outside the apparatus with power supply to the main control unit reduced or cut off, to the packet received by the communication unit without awaking the main control unit.
In Japanese Patent Application Laid-Open No. 2009-151537, by allowing the main control unit to shift to a power saving state, a reduction in power consumption of the image forming apparatus can be achieved. However, Japanese Patent Application Laid-Open No. 2009-151537 does not pay any attention to allowing the communication unit to shift to a power saving state. In Japanese Patent Application laid-Open No. 2009-151537, the communication unit is not in a power saving state even if the communication unit waits for receiving a packet. Therefore, power is uselessly consumed when the communication unit waits for receiving the packet.